The present invention relates to a rubber composition which is suitable for tire treads having excellent wet grip performance.
A higher stability at high speed has been so far required for tires with the development of a highway network, and particularly enhancement of grip performance on a wet road has been required.
For example, JP-A-6-1882, JP-A-6-240050, JP-A-9-241430 and JP-A-9-241426 disclose that mainly from the viewpoint of enhancing wet skid characteristics, ozone resistance and flexibility, a halogenated butyl rubber and a brominated copolymer of isomonoolefin and paramethylstyrene are used as a rubber component and carbon black is added as a reinforcing material.
Recently from the viewpoint of enhancing wet grip performance, silica is added instead of a part or the whole of carbon black.
In that case, in the rubber composition containing silica, since dispersibility of silica is low, there was a problem that characteristics of silica such as an enhancement of abrasion resistance and wet grip performance cannot be exhibited sufficiently.
An object of the present invention is to obtain a rubber composition for tire treads which comprises a rubber component containing a brominated isobutylene/ paramethylstyrene copolymer and a specific wet silica and has an enhanced wet grip performance.